My current setup for recording acoustic guitar is to use an SM-57 and, depending on the music, either mix in the input from my condenser mic for room sound (a Studio Projects C-1) or mix in the input from the pickup.
I'll be recording a solo musician in a few weeks who prefers to record live -- female vocal and steel-string guitar together -- so I'm looking at a three-mic setup. (Her guitar has no pickup or internal mic.) The audio interface I currently use have only has two inputs. She's looking for a close-miked detailed sound.
The obvious solution is to run the external mics into a mixing board then into the interface. Are there any single-mic solutions that would cost less than a couple hundred dollars? The SM-57, while a great mic, doesn't pick up anywhere near the amount of detail that a good condenser mic does, and the C-1 I have is far too wide-area a mic for this. (The SM-81 looks sweet, but a bit too pricey just now.)
The room I record in is fairly dead, but unfortunately has a little background noise, so mics with fairly tight patterns work best.